Exhaust Treatment System for Internal Combustion Engine

ABSTRACT

An exhaust treatment system for an internal combustion engine comprises an exhaust gas conduit configured to receive an exhaust gas from the internal combustion engine and to deliver the exhaust gas to an exhaust treatment device. A fluid delivery system is located upstream of the exhaust treatment device and is configured to deliver a fluid thereto. It comprises a fluid injector, a fluid tube in fluid communication with the fluid injector and extending radially into the exhaust gas conduit for receipt of fluid from a spray tip of the fluid injector, a controller configured to energize the fluid injector to deliver fluid to the fluid tube, and opening(s) in the tube, disposed beyond the boundary layer of exhaust gas flow in the exhaust gas conduit, for release of the fluid into the exhaust gas flow.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application claims priority to U.S. Patent Application Ser.No. 61/680,826 filed Aug. 8, 2012 which is hereby incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

Exemplary embodiments of the invention relate to exhaust treatmentsystems for internal combustion engines and, more particularly, toexhaust treatment systems capable of fully mixing and vaporizinginjected fluids into the exhaust gas flow for improved performancethereof.

BACKGROUND

Manufacturers of internal combustion engines must satisfy customerdemands while meeting various government regulations for reducedemissions and improved fuel economy. One example of a way to improvefuel economy is to operate an engine at an air/fuel ratio that is lean(an excess of oxygen) of stoichiometry. Examples of such lean-burnengines include compression ignition engines (diesel) and lean-burnspark-ignition engines. However, while lean burn engines may haveimproved fuel economy, the exhaust gas emitted from such an engine,particularly a diesel engine, may be a heterogeneous mixture thatincludes gaseous emissions such as carbon monoxide (“CO”), unburnedhydrocarbons (“HC”) and oxides of nitrogen (“NOx”) as well as condensedphase materials (liquids and solids) that constitute particulate matter(“PM”). Catalyst compositions typically disposed on catalyst supports orsubstrates are provided in various exhaust system devices to convertcertain, or all of these exhaust constituents into non-regulated exhaustgas components.

An exhaust treatment technology in use for high levels of particulatematter reduction, particularly in diesel engines, is the DieselParticulate Filter (“DPF”) device. There are several known filterstructures used in DPF devices that have displayed effectiveness inremoving the particulate matter from engine exhaust gas such as ceramichoneycomb wall flow filters, wound or packed fiber filters, open cellfoam filters, sintered metal foams, etc. Ceramic wall flow filters haveexperienced significant acceptance in automotive applications.

The filter is a structure for removing particulates from the exhaust gasand, as a result, the accumulation of filtered particulate matter willeventually have the effect of increasing the exhaust system backpressureexperienced by the engine. Such increase in backpressure will eventuallyhave a negative impact on engine performance and fuel economy. Toaddress exhaust system backpressure increases caused by the accumulationof particulate matter, the DPF device is periodically cleaned, orregenerated. Regeneration of a DPF device in vehicular applications istypically automatic and is carried out by an engine or other controllerbased on signals received by engine and exhaust system sensors. Theregeneration event typically involves raising the temperature of the DPFdevice to levels that are often above 600 C in order to burn theaccumulated particulates thereby cleaning the DPF device.

One method of generating the temperatures required in the exhaust systemfor regeneration of the DPF device is to deliver unburned HC, often inthe form of raw fuel to an oxidation catalyst (“OC”) device that isdisposed upstream of the DPF device. The OC device typically carries anoxidation catalyst compound which aides in oxidizing HC in an exothermicevent which raises the temperature of the exhaust gas. The heatedexhaust gas travels downstream to the DPF device where it burns theparticulates trapped therein. Injection of the fuel into the exhausttreatment system is often carried out using injection devices similar tofuel injectors used in engines. A common challenge for exhaust systemdesigners is to inject the HC upstream of the OC device in a manner thatallows for the HC to fully disperse in order to utilize the entire OCfor oxidation and to fully vaporize so as to completely combust as itpasses through the OC device.

Accordingly it is desirable to provide an HC delivery system thatachieves substantially uniform mixing, distribution and vaporization ofa fluid injected into the exhaust gas of an exhaust gas treatmentsystem.

SUMMARY

In an exemplary embodiment, an exhaust treatment system for an internalcombustion engine comprises an exhaust gas conduit configured to receivean exhaust gas from the internal combustion engine and to deliver theexhaust gas to an exhaust treatment device. A fluid delivery system islocated upstream of the exhaust treatment device and is configured todeliver a fluid thereto. The fluid delivery system comprises a fluidinjector, a fluid tube in fluid communication with the fluid injectorand extending radially into the exhaust gas conduit for receipt of fluidfrom a spray tip of the fluid injector, a controller configured toenergize the fluid injector to deliver fluid to the fluid tube, and anopening in the tube, disposed beyond the boundary layer of exhaust gasflow in the exhaust gas conduit, for release of the fluid into theexhaust gas flow.

The above feature and advantages and other features and advantages ofthe invention are readily apparent from the following detaileddescription of the invention when taken in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS AND APPENDIX

FIG. 1 is a schematic view of an engine and exhaust treatment systemembodying features of the invention;

FIG. 2, including FIGS. 2A-2H, are an enlarged portion of the exhaustsystem of FIG. 1 including examples of fluid tubes embodying features ofthe invention;

FIG. 3 is a flow diagram illustrating flow characteristics and otherfeatures of the invention;

FIG. 4 is another example of a fluid tube embodying features of theinvention;

FIG. 5 is another example of a fluid tube embodying features of theinvention;

FIG. 6 is another example of a fluid tube embodying features of theinvention;

FIG. 7 is another example of a fluid tube embodying features of theinvention;

FIG. 8 is a flow diagram illustrating further flow characteristics andother features of the invention; and

FIG. 9 is an illustration, partially in section, of an injector andfluid tube embodying features of the invention.

DESCRIPTION OF THE EMBODIMENTS

The following description is merely exemplary in nature and is notintended to limit the present disclosure, its application or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

Referring to FIG. 1, an exemplary embodiment of the invention isdirected to an exhaust gas treatment system 10, for the reduction ofregulated exhaust gas constituents emitted from an internal combustionengine, such as diesel engine 12. It is appreciated that the dieselengine 12 is merely exemplary and that the invention described can beimplemented in various engine systems requiring an exhaust gasparticulate filter. For ease of description, the disclosure will bediscussed in the context of diesel engine 12.

The exhaust gas treatment system 10 includes an exhaust gas conduit 14,which may comprise several segments, that functions to transport exhaustgas 16 from the diesel engine 12 to the various exhaust gas treatmentdevices of the exhaust gas treatment system. In an exemplary embodiment,the exhaust treatment devices may include a first oxidation catalystdevice (“OC1”) 18. The OC1 18 may include a flow-through metal orceramic monolith substrate 20 that is wrapped in an intumescent mat (notshown) that expands when heated, securing and insulating the substrate20. The substrate 20 is packaged in a rigid shell or canister having aninlet and an outlet in fluid communication with exhaust gas conduit 14.The substrate 20 has an oxidation catalyst compound (not shown) disposedthereon. The oxidation catalyst compound may be applied as a washcoatand may contain platinum group metals such as platinum (Pt), palladium(Pd), rhodium (Rh) or other suitable oxidizing catalyst, or combinationthereof. The OC1 18 is useful in treating unburned gaseous andnon-volatile HC and CO, which are oxidized to form carbon dioxide andwater.

A selective catalytic reduction device (“SCR”) 22 may be disposeddownstream of the OC1 18. In a manner similar to the OC1, the SCR 22 mayalso include a flow-through ceramic or metal monolith substrate 24 thatis wrapped in an intumescent mat (not shown) that expands when heated,securing and insulating the substrate 24. The substrate 24 is packagedin a rigid shell or canister having an inlet and an outlet in fluidcommunication with exhaust gas conduit 14. The substrate 24 has an SCRcatalyst composition (not shown) applied thereto. The SCR catalystcomposition preferably contains a zeolite and one or more base metalcomponents such as iron (“Fe”), cobalt (“Co”), copper (“Cu”) or vanadium(“V”) which can operate efficiently to convert NO_(x) constituents inthe exhaust gas 16 in the presence of an injected exhaust fluid such asan ammonia (“NH₃”) reductant 26. The NH₃ reductant 26, supplied fromreductant supply tank 28 through conduit 30, may be injected into theexhaust gas conduit 14 at a location upstream of the SCR 22 using afluid delivery system 32 to be described below. The reductant may be inthe form of a liquid or an aqueous urea solution when it is delivered tothe exhaust gas 16 by the fluid delivery system 32. A mixer orturbulator 50 may also be disposed within the exhaust conduit 14 inclose downstream proximity to the fluid delivery system to furtherassist in thorough mixing of the reductant 26 with the exhaust gas 16.

In one exemplary embodiment, an exhaust gas filter assembly, in thiscase a diesel particulate filter device (“DPF”) 34 is located within theexhaust gas treatment system 10, downstream of the SCR 22 and operatesto filter the exhaust gas 16 of carbon and other particulates. The DPF34 may be constructed using a ceramic wall-flow monolith filter 36 thatis wrapped in an insulating mat that secures and insulates the filter36. The filter 36 may be packaged in a rigid shell or canister having aninlet and an outlet in fluid communication with exhaust gas conduit 14.Exhaust gas 16 entering the filter 36 is directed to migrate throughadjacent longitudinally extending walls (not shown) and, it is throughthis wall-flow mechanism that the exhaust gas 16 is filtered of carbonand other particulates. The filtered particulates are deposited in thefilter 36 and, over time, will have the effect of increasing the exhaustgas backpressure experienced by the diesel engine 12. It is appreciatedthat a ceramic wall-flow monolith filter 36 is merely exemplary innature and that the DPF 34 may include other filter devices such aswound or packed fiber filters, open cell foams, sintered metal fibers,etc.

In an exemplary embodiment, the increase in exhaust backpressure causedby the accumulation of particulate matter requires that the DPF 34 beperiodically cleaned, or regenerated. Regeneration involves theoxidation or burning of the accumulated carbon and other particulates inwhat is typically a high temperature (>600° C.) and excess oxygenenvironment. For regeneration purposes a second oxidation catalystdevice (“OC2”) 38 may be located upstream of the filter 36, proximate toits upstream end. In the embodiment illustrated in FIG. 1, the OC2 38 isa flow-through metal or ceramic monolith substrate 40 that is wrapped inan intumescent mat (not shown) that expands when heated, securing andinsulating the substrate 40. The substrate 40 is packaged in thecanister of the DPF 34. The substrate 40 has an oxidation catalystcompound (not shown) disposed thereon. The oxidation catalyst compoundmay be applied as a wash coat and may contain platinum group metals suchas platinum (Pt), palladium (Pd), rhodium (Rh) or other suitableoxidizing catalysts, or combination thereof. While the embodimentdescribed includes the OC2 38 disposed in the canister of the DPF 34, itis contemplated that, depending on packaging and other systemconstraints, the OC2 38 may also be disposed within a separate canister(not shown) that is located upstream of the DPF 34. In an otherembodiment, the OC2 38 and the DPF 36 may also be in a common orseparate canisters(s) and be located in a close coupled positionrelative to the engine turbocharger or exhaust conduit 14, with the SCRcatalyst 24 being located downstream of the OC2/DPF.

Disposed upstream of the DPF 34, in fluid communication with the exhaustgas 16 in the exhaust gas conduit 14, is a fluid delivery system 42 tobe described below. The fluid delivery system 42, in fluid communicationwith HC fluid 44 in fuel supply tank 46 through fuel conduit 48, isconfigured to introduce unburned HC fluid 44 (raw fuel) into the exhaustgas stream for delivery to the OC2 38 associated with the DPF 34. Amixer or turbulator 50 may also be disposed within the exhaust conduit14, in close, downstream proximity to the fluid delivery system 42, tofurther assist in thorough mixing, breakup, vaporization anddistribution of the HC with the exhaust gas 16.

A controller such as vehicle controller 52, for example, is operablyconnected to, and monitors, the exhaust gas treatment system 10 throughsignal communication with a number of sensors. As used herein the termcontroller may include an application specific integrated circuit(ASIC), an electronic circuit, a processor (shared, dedicated or group)and memory that executes one or more software or firmware programs, acombinational logic circuit, and/or other suitable components thatprovide the described functionality. In an exemplary embodiment, abackpressure sensor 54, located upstream of DPF 34 or between OC 38 andturbulator 50, generates a signal indicative of the carbon andparticulate loading in the ceramic wall flow monolith filter 36. Thispressure sensor 54 may also be of a delta pressure type with thedownstream part located after the DPF 36. Upon a determination that theparticulate loading in the DPF (which may be determined by a signal thatthe backpressure has reached a predetermined level indicative of theneed to regenerate the DPF 34), the controller 52 activates the fluiddelivery system 42 to deliver HC fluid 44 into the exhaust gas conduit14 for mixing with the exhaust gas 16. The fuel/exhaust gas mixtureenters the OC2 38 inducing oxidation of the HC fluid 44 in the exhaustgas 16 and raising the exhaust gas temperature to a level (e.g. >600°C.) suitable for regeneration of the carbon and particulate matter inthe filter 36. The controller 52 may monitor the temperature of theexothermic oxidation reaction in the OC2 38 and the ceramic wall-flowmonolith filter 36 through temperature sensor 56 and adjust the HCdelivery rate of fluid delivery system 42 to maintain a predeterminedtemperature depending on many factors such as temperature upstream ofthe OC 38, the exhaust mass flow rate 16, etc.

Referring now to FIGS. 2 and 3, with continuing reference to FIG. 1, thefluid deliver systems 32 and 42 will now be described in detail. Forease of description, the following discussion will focus on the HC fluiddelivery system 42, however it should be understood the descriptionapplies equally to the delivery of NH3 reductant to the exhaust gastreatment system 10 by fluid delivery system 32. In an exemplaryembodiment, an enlarged portion of the exhaust treatment system 10illustrates exhaust gas conduit 14 adjacent to the inlet end 60 of theDPF device 34 which, in the exemplary embodiment described above housesthe OC2 38 directly upstream of the ceramic wall-flow monolith filter36. In the embodiment shown, the fluid delivery system 42 comprises atleast one HC atomizer 62 that is mounted in an opening in the exhaustgas conduit 14. The HC atomizer 62, which may be an injector, vaporizer,or pump, is in fluid communication with a fluid tube 64, extendingradially into the exhaust gas conduit 14, and receives atomized HC fluid44 through the spray tip 66 of the HC atomizer 62. In exemplaryembodiments, there may be more than 1 spray tip. When the HC atomizer 62is energized by the controller 52 upon determination that the ceramicwall flow monolith filter 36 of the DPF device 34 requires regeneration.HC fluid 44 enters the fluid tube 64 and is heated due to the placementof the tube in the exhaust gas flow, which assists in the vaporizationof the HC fluid 44. Additionally the fuel passes through the fluid tubeand past the slower moving boundary layer of exhaust gas 16 near theouter circumference 68 of the exhaust gas conduit 14 and is placed in alocation of exhaust gas 16 which is favorable for good mixing and avariety of exhaust flow conditions. In one embodiment, the HC fluid 44enters the exhaust gas 16 from a position centrally located within theconduit 14.

HC fluid openings 70A, 70B are located in the fluid tube 64 at variouslocations along the length of the fluid tube 64. These openings 70A, 70Bmay face upstream, into the oncoming flow of the exhaust gas 16,downstream, away from the flow of the exhaust gas or they may be placedin a tangential orientation to the flow of the exhaust gas. The numberand placement of the HC fluid openings 70A, 70B may be determined by theexhaust flow rate (i.e. velocity, flow volume) of the particular engine12 and exhaust treatment system 10 as well as the configuration (i.e.diameter, etc.) of the exhaust gas conduit 14 at the location at whichthe fluid tube 64 is placed. Upstream facing openings 70A allow theexhaust gas 16 to enter the fluid tube 64 and entrain the HC fluid 44for flow out of downstream facing openings 70B for example FIGS.2A,B,C,D,F,G,H. Downstream only openings 70B, FIG. 2E, utilize a vacuumcreated by flow around the fluid tube 64 to pull or extract the HC fluid44 vapor into the exhaust gas 16 flowing around the fluid tube 64 butthe HC fluid 44 vapor is mainly motivated for flow into the exhaustconduit 14 by the fuel flow from the atomizer and temperature in theexhaust causing the HC fluid 44 to vaporize and greatly expand. Asillustrated in FIGS. 2A, B, F, G, H, and FIG. 3 a series of HC fluidopenings 70A, 70B distributed along the length of the fluid tube 64 willallow HC fluid 44 vapor to be substantially evenly distributed acrossthe diameter of the exhaust gas conduit 14 and, thus the exhaust gasflow 16. In one embodiment, HC fluid 44 vapor is distributed across acentral portion of the exhaust gas flow 16. It should be appreciatedthat, HC fluid openings 70A, 70B that are more centrally concentratednear the centerline of the exhaust gas conduit 14 will disperse the HCfluid 44 into the highest velocity portion of the exhaust gas flow 16.The determination of which design of tube to use may also be determinedby the type, number and location of the mixer(s) 50 chosen for anyparticular application as well as the diameter (area) of gas conduit 14(which may be variable along its length) and the distance of the fluidtube 64 from the OC 38.

Referring again to FIG. 2 the fuel tube 64 may extend across the entirediameter of the exhaust gas conduit 14 or only partially there across.In such instances in which the tube extends across the entire diameterof the exhaust gas conduit, an option exists to add a second HC atomizer62 and spray tip 66, FIGS. 2A, B, C, D, E and F2 at the opposite ordistal end from the first HC atomizer 62 and spray tip 66. In suchinstances, further fuel control or resolution is provided to thecontroller 52 during regeneration. However, there may be cost or designadvantages to have the fuel tube 64 extend only partially across thediameter of the exhaust gas conduit as illustrated in FIGS. 2G and H. Insuch case one HC atomizer 62 and spray tip 66 is utilized to deliverfuel to the exhaust gas stream 16 flow through the exhaust gas conduit14.

Referring now to FIGS. 4-7, with continuing reference to FIG. 1, anotherexemplary embodiment of the fluid delivery systems 32 and 42 will now bedescribed in detail. Similarly, for ease of description, the followingdiscussion will focus on the HC fluid delivery system 42, however itshould be understood that the description applies equally to thedelivery of NH₃ reductant to the exhaust gas treatment system 10. In anexemplary embodiment, as shown in FIG. 2, the exhaust gas conduit 14 maybe adjacent to the inlet end 60 of the DPF device 34 which houses theOC2 38 directly upstream of the ceramic wall-flow monolith filter 36. Inthe embodiment shown, the fluid delivery system 42 comprises at leastone HC injector 80 that is mounted in an opening in the exhaust gasconduit 14 in a known manner. The HC injector 80 is in fluidcommunication with fuel passages 86, FIGS. 4-7, of fluid tube 64. Thefuel passages 86 receive injected HC fluid 44 when the injector isenergized by the controller 52 upon determination that the ceramic wallflow monolith filter 36 of the DPF device 34 requires regeneration. Thefuel passages 86 may be drilled into a solid fluid tube 64 withintersecting outlet portions 87 also drilled at various locations alongthe length thereof. Once HC fluid 44 enters the fuel passages 86 in thefluid tube 64 it is heated due to the placement of the fluid tube 64 inthe exhaust gas flow, which assists in the vaporization of the HC fluid44. Additionally the fuel passes through the fuel passages in the fluidtube 64 and past the slower moving boundary layer of exhaust gas 16 nearthe outer circumference 68, FIG. 3, of the exhaust gas conduit 14. Inexemplary embodiments, having multiple passages 86 (FIGS. 5, 6 and 7)provide advantages for better distribution the HC fluid 44 from spraytip 66.

Fuel passages 86 open at various locations along the length of the fluidtube 64, FIGS. 5-7. The fluid passages 86 may face upstream, into theoncoming flow of the exhaust gas 16, downstream, away from the flow ofthe exhaust gas 16 or they may be placed in a tangential orientation tothe flow of the exhaust gas. The number and placement of the fluidpassages 86 will be determined by the exhaust flow rate (i.e. velocity,flow volume) of the particular engine 12 and exhaust treatment system 10as well as the configuration (i.e. diameter, etc.) of the exhaust gasconduit 14 at the location at which the fluid tube 64 is placed. Thedetermination of which design tube to use will also be matched to thetype, number and location of the mixer(s) 50 chosen for any particularapplication as well as the diameter (area) of gas conduit 14 (which maybe variable down the length) and the distance of the fluid tube 64 fromthe OC 38.

As illustrated in FIGS. 5-7, a series of fluid passages 86 opening alongthe length of the fluid tube 64 will allow HC fluid 44 to be evenlydistributed across the diameter of the exhaust gas conduit and, thus theexhaust gas flow 14. It should be appreciated that fuel openings thatare more centrally concentrated near the centerline of the exhaust gasconduit 14 as in FIG. 4 will disperse the HC fluid 44 into the highestvelocity portion of the exhaust gas flow 16.

Referring now to FIG. 8, the effect of the fluid tube 64 on the flow ofexhaust gas 16 can be seen. As the exhaust gas passes the fluid tube 64a turbulent wake region 88 is created. In cases in which the fuel tube64 includes HC fluid openings or fluid passages that face in thedownstream or tangential direction, additional fuel mixing is encouragedin the wake region 88 due to added turbulence as well as residence timeof that gas as it slows momentarily. It is contemplated as isillustrated in FIG. 8, that different fluid tube cross sections 89A-89Dmay be used. The diameter of the tube 64 will be chosen to accentuatethis effect in relation the exhaust conduit 14 area and the exhaust flowrange for the application.

Referring now to FIG. 9, in an exemplary embodiment, an exhaust boss 90is fixed externally to the exhaust conduit 14 and defines a through-hole92 for fluid access to the exhaust gas flow 16. The fluid tube 64 isinserted through the exhaust boss 90 through hole 92 and is supported inthe through hole 92 by a flared upper end 94. The flared upper end 94receives the spray tip 66 of the HC atomizer 62 or the injector tip 82of the HC injector 80 and is subsequently locked in place by a gland nut96 which is threated into the exhaust boss 90.

In exemplary embodiments, the distance from the atomizer 62 and the fueltube 64 to the OC 38, the design of the tube, and the design locationand number of mixers 50 may be varied based on the type of the engine 12and the desired performance characteristics of the exhaust gas treatmentsystem 10.

While the invention has been described with reference to exemplaryembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiments disclosed but that theinvention will include all embodiments falling within the scope of thepresent application.

What is claimed is:
 1. An exhaust treatment system for an internal combustion engine comprising: an exhaust gas conduit configured to receive an exhaust gas from the internal combustion engine and to deliver the exhaust gas to an exhaust treatment device; a fluid delivery system located upstream of the exhaust treatment device and configured to deliver a fluid thereto, the fluid delivery system comprising: a fluid injector; a fluid tube in fluid communication with the fluid injector and extending into the exhaust gas conduit for receipt of fluid from a spray tip of the fluid injector; a controller configured to energize the fluid injector to deliver fluid to the fluid tube; and an opening in the tube, centrally disposed within exhaust gas flow in the exhaust gas conduit, for release of the fluid into the exhaust gas flow.
 2. The exhaust treatment system of claim 1, the exhaust treatment device comprising an oxidation catalyst and the fluid comprising unburned hydrocarbon.
 3. The exhaust treatment system of claim 1, the exhaust treatment device comprising an selective catalytic reduction device and the fluid comprising an ammonia (“NH₃”) reductant.
 4. The exhaust treatment system of claim 1, wherein the fluid tube extends diametrically across the diameter of the exhaust gas conduit having a second end in communication with the exhaust gas conduit.
 5. The exhaust treatment system of claim 4, comprising a second fluid injector in communication with the second end of the fluid tube to deliver fluid to the fluid tube.
 6. The exhaust treatment system of claim 1, wherein the fluid injector is a fluid vaporizer.
 7. The exhaust treatment system of claim 1, further comprising multiple openings located at locations along the length of the tube.
 8. The exhaust treatment system of claim 7, further comprising upstream facing openings configured to allow the exhaust gas to enter the fluid tube and entrain the fluid and downstream facing downstream facing openings configured for the flow of fuel and exhaust gas out of the fluid tube.
 9. The exhaust treatment system of claim 1, wherein the fluid tube extends radially into the exhaust gas conduit.
 10. The exhaust treatment system of claim 1, wherein the opening in the tube is centrally disposed beyond the boundary layer of exhaust gas flow in the exhaust gas conduit.
 11. A fluid delivery system configured to deliver a fluid to an exhaust treatment device via an exhaust gas conduit, the fluid delivery system comprising: a fluid injector; a fluid tube in fluid communication with the fluid injector and extending into the exhaust gas conduit for receipt of fluid from a spray tip of the fluid injector; a controller configured to energize the fluid injector to deliver fluid to the fluid tube; and an opening in the tube, centrally disposed within the exhaust gas conduit, for release of the fluid into the exhaust gas conduit.
 12. The fluid delivery system of claim 11, wherein the fluid tube extends diametrically across the diameter of the exhaust gas conduit having a second end in communication with the exhaust gas conduit.
 13. The fluid delivery system of claim 12, comprising a second fluid injector in communication with the second end of the fluid tube to deliver fluid to the fluid tube.
 14. The fluid delivery system of claim 11, wherein the fluid injector is a fluid vaporizer.
 15. The fluid delivery system of claim 11, further comprising multiple openings located at locations along the length of the tube.
 16. The fluid delivery system of claim 15, further comprising upstream facing openings configured to allow the exhaust gas to enter the fluid tube and entrain the fluid and downstream facing downstream facing openings configured for the flow of fuel and exhaust gas out of the fluid tube.
 17. The fluid delivery system of claim 11, wherein the fluid tube extends radially into the exhaust gas conduit.
 18. The fluid delivery system of claim 11, wherein the opening in the tube is centrally disposed beyond the boundary layer of exhaust gas flow in the exhaust gas conduit. 